Box level

ABSTRACT

A level including an elongate hollow frame with two sidewalls and a topwall extending therebetween. A topnotch is formed by removal of a topwall section and adjacent sections of sidewalls including notch-defining bottom and side edges. A central vial is within the topnotch. The frame includes an inner horizontal wall extending between the sidewalls at the notch-defining bottom edges. A central-vial reference surface is formed in the inner horizontal wall parallel to the top and bottom measuring surfaces and defining a notch-bottom. The central vial is supported against the central-vial reference surface in accurate orientation without calibration. The central vial is secured with respect to the inner horizontal wall by mechanical fasteners. The frame further preferably includes an integral inner vertical wall extending between the top and bottom walls thereby reinforcing the frame along the frame length.

RELATED APPLICATION

This application is a continuation of patent application Ser. No.12/913,086, filed Oct. 27, 2010, now U.S. Pat. No. 8,375,591, issuedFeb. 19, 2013, which is based in part on U.S. Provisional ApplicationNo. 61/256,264, filed Oct. 29, 2009, and on U.S. Provisional ApplicationNo. 61/259,038, filed Nov. 6, 2009. The entire contents of the parentapplication Ser. Nos. 12/913,086, 61/256,264 and 61/259,038 areincorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to levels and, more particularly, to structuresfor accurate vial installation and reinforcement of the level frame.

BACKGROUND OF THE INVENTION

In heavy-duty levels it is important that the frame of the levelmaintains stability for accurate measurement readings. It is alsoimportant that levels, which are used in professional construction ontypes of jobs when a level may be dropped from a substantial height andbe subjected to various stresses, sustain the impact with minimal or nodamage.

Many box levels have a central vial positioned into a notch which isformed by removing a section of a top wall and adjacent portions of eachside wall, as seen in FIG. 1.

Because material is removed from the center of the frame, a centralframe section becomes the weakest portion of the extrusion. Tests haveshown that in prior levels 10, the central region 11 of a frame 12 withthe cut-out notch portion 20 for the central vial is substantially weak.FIG. 2 shows that in such prior levels 10 a bottom 21 of the notch 20 isthe weakest region. Portions 22 of sidewalls 13 which surround thecentral-vial notch 20 are also substantially weak regions 22A whichextend to weakened areas 22B.

It is further seen in FIG. 2 that there is also a substantial weaknessin topwall regions 23 adjacent to hand holes from which material is alsoremoved from the level frame 12. There is a need for an improved levelwith a strong stable frame.

Levels include plural vials, almost always including a principal centervial which is parallel to a reference surface and used to indicate ahorizontal orientation. Such horizontal vial is normally secured to thelevel frame in a position that permits viewing of the vial from bothsides and also from above to ascertain the orientation of substantiallyhorizontal surfaces. The most desirable positioning of such vial iswithin a topnotch in the body of a level which topnotch is defined bytwo sidewalls and the topwall of a hollow level body frame. However,such positioning also presents a challenge for accurate securing of thevial to the frame. Such installation involves multiple steps, includingcalibration for accurate measurements. There is a need for an improvedlevel which allows simple accurate mounting of the vial to the levelbody.

OBJECTS OF THE INVENTION

It is an object of the invention to provide an improved level whichovercomes some of the problems and shortcomings of the prior art,including those referred to above.

Another object of this invention is to provide a level with a strongstable frame even in areas of material removal.

Another object of the invention is to provide a level which allowsaccurate mounting of the vial(s) to the level body.

Still another object of the invention is to provide a level whichfacilitates simple calibration-free mounting of vial(s) with respect tothe frame.

Yet another object of the invention is to provide a method for securingvial(s) to a level.

How these and other objects are accomplished will become apparent fromthe following descriptions and the drawings.

SUMMARY OF THE INVENTION

This invention, which will be described in detail below, is animprovement in levels of the type including an elongate hollow framewith two sidewalls and top and bottom walls which extend between thesidewalls and define top and bottom measuring surfaces. A topnotch isformed by removal of a topwall section and adjacent sections ofsidewalls including notch-defining bottom and side edges. A central vialis within the topnotch.

In the inventive level, the frame includes an inner horizontal wallextending between the sidewalls at the notch-defining bottom edges. Acentral-vial reference surface is formed in the inner horizontal wallparallel to the top and bottom measuring surfaces and defining anotch-bottom. The central vial is supported against the central-vialreference surface in accurate orientation without calibration. It ispreferred that the central vial be secured with respect to the innerhorizontal wall by mechanical fasteners. In preferred embodiments, thehollow frame is an extrusion with the inner horizontal wall beingintegral with the sidewalls thereby reinforcing the frame weakened bythe removal of the topwall section to form the topnotch.

The extrusion further preferably includes an integral inner verticalwall extending between the top and bottom walls thereby reinforcing theframe along the frame length. The level further includes an end vialwithin an end-vial opening formed through the sidewalls and the innervertical wall. The vertical wall preferably defines end-vial referencesfor calibration-free accurate positioning of the end vial within theframe.

The inventive level preferably includes an external brace having a pairof plate members each against one of the sidewalls about thenotch-defining bottom and side edges and each substantially spanning arespective one of the sidewalls. A fastening member extends through thesidewalls and pulls the plate members toward each other to sandwich thesidewalls therebetween, thereby further reinforcing a central frameportion weakened by the topnotch.

Another aspect of the invention is a method for calibration-freemanufacturing of the inventive level. The inventive method includes thesteps of providing an inner horizontal wall extending between thesidewalls at the notch-defining bottom edges; simultaneously formingparallel top and bottom measuring surfaces and a notch-bottom surfacewhich is precisely parallel to each measuring surface; placing acentral-vial structure on the notch-bottom surface which assurescentral-vial accurate orientation without calibration; and securing thecentral-vial structure with respect to the frame. It is preferred thatthe central-vial structure be secured to the inner horizontal wall withmechanical fasteners and free of adhesive.

The step of simultaneously forming parallel surfaces is preferably by asingle step of CNC machining of the top and bottom walls and the innerhorizontal wall.

The method may further include the steps of providing an external braceincluding a pair of plate members each configured to substantially spanone of the sidewalls about the notch-defining edges; positioning eachplate member against a respective one of the sidewalls about thenotch-defining edges; and securing the external brace to the frame witha fastening member extending through the sidewalls and pulling the platemembers toward each other to sandwich the sidewalls therebetween,thereby reinforcing a central frame portion weakened by the topnotch.

The hollow frame is an extrusion with the inner horizontal wall beingintegral with the sidewalls thereby reinforcing the frame weakened bythe removal of the topwall section to form the topnotch. The methodpreferably includes further steps of providing an integral innervertical wall extending between the top and bottom walls therebyreinforcing the frame along the frame length; simultaneously forming anend-vial opening and an end-vial mounting reference which assurescalibration-free accuracy of the end vial orientation; positioning anend vial within the opening according to the end-vial mountingreferences; and securing the end vial with respect to the frame. The endvial is preferably secured with respect to the frame with mechanicalfasteners and free of adhesive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary perspective view of a prior level showing atop-notch material removal.

FIG. 2 is a fragmentary perspective view of a prior level frame showingweak regions around material removal for central-vial top notch andhand-hold holes.

FIG. 3 is a perspective view of the frame of the inventive level showinginner walls.

FIG. 4 is a fragmentary perspective end view of the frame of the levelof FIG. 3 showing material removal for central-vial top notch andhand-hold holes.

FIG. 5 is a fragmentary perspective side view of the level frame of FIG.5, showing strengthening of the weak regions around material removal.

FIG. 6 is a comparison table reflecting test results showing increase inframe strength in the inventive level frame of FIG. 5.

FIG. 7 is a fragmentary perspective view of the inventive level frameshowing precisely parallel surfaces for a calibration-free installationof the central vial.

FIG. 8 is an exploded fragmentary perspective view showing one versionof the calibration-free installation of the central vial to the levelframe of FIG. 7.

FIGS. 9-12 are exploded fragmentary perspective views of the inventivebox level showing different stages of calibration-free installation ofthe central vial and exterior strengthening of the central region of thelevel frame.

FIGS. 13 and 15 are fragmentary perspective views of the central regionof the inventive level assembled as shown in FIGS. 9-12.

FIG. 14 is a fragmentary perspective view of the central region of theinventive level and showing precise calibration-free installation of thecentral vial.

FIG. 16 is a fragmentary perspective view of the central region of theinventive level of FIG. 15 in more detail.

FIG. 17 is a fragmentary perspective view of the central region ofpartially-assembled inventive level showing strengthening by theexternal reinforcement of the central region.

FIG. 18 is a comparison table reflecting test results for increase inframe strengthening in the inventive level frame of FIG. 5 compared tothe inventive level frame of FIG. 17 and to a prior art level.

FIG. 19 is a fragmentary perspective view of the end-vial region of theinventive level, and showing calibration-free installation of the endvial.

FIG. 20 is a fragmentary perspective view of the end-vial region of theinventive level showing an improved-visibility plumb vial.

FIG. 20A is an exploded view of the end-vial structure of the inventivelevel of FIG. 20.

FIG. 20B is cross-sectional view of the inventive plumb-vial assemblyalong a horizontal section plane.

FIGS. 21 and 22 are fragmentary perspective views of the inventive leveland illustrating high-visibility plumb vial aspect of the presentinvention.

FIG. 23 is a detailed fragmentary perspective view of the end-vialregion of the inventive level showing an improved-visibility plumb vialand an improved end cap.

FIG. 24 is an end view of the inventive level, showing a grippingextension of the plumb-vial assembly.

FIG. 25 is a fragmentary perspective view showing details of theimproved end cap.

FIG. 26 is a front perspective views of the inventive level shown inresting position against a vertical surface.

FIG. 27 is a side perspective views of the inventive level shown inresting position against a vertical surface.

FIGS. 28 and 29 are fragmentary perspective views showing an improvedhand grip of the inventive level.

FIG. 30 is a perspective view of the inventive level.

FIG. 31 is a front elevation of the inventive level.

FIG. 32 is a cross-section of the inventive level taken along ahorizontal plane.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 3-5, 7-17 and 19-32 illustrate an inventive level 100 whichincludes an elongate hollow frame 120 with two sidewalls 180, a top wall130 and a bottom wall 140 which extend between sidewalls 180 and definetop and bottom measuring surfaces. A topnotch 20 is formed by removal ofa topwall section and adjacent sections of sidewalls includingnotch-defining bottom and side edges. A central vial 50 is withintopnotch 20.

In inventive box level 100, level frame 120 includes an internalhorizontal wall 30. As seen in FIGS. 3 and 4, such internal horizontalwall 30 is substantially parallel to top wall 130 and is spaced from topwall 130 for a distance 31 necessary for installation of a central vial50. FIG. 4 shows that this internal horizontal wall 30 is entirelyremoved in portions of level frame 120 to form hand-holes 150 and inareas 160 for installation of end vials such as plumb vials 40.

Because of its specific location along bottom 21 of central-vial notch20, internal horizontal wall 30 significantly strengthens the centralregion 170 of frame 120 which has been weakened by the material removal.

FIGS. 3 and 4 further show that frame 120 of inventive box level 100further includes an internal vertical wall 35. Such vertical internalwall 35 adds rigidity to entire frame 120 and strengthens areas withmaterial removal and where horizontal wall 30 is not present, includingaround hand holes 150 and plumb-vial holes 160, as seen in FIG. 4.

FIG. 5 shows that in inventive box level 100 the weakness of thecentral-vial notch region 20 is reduced to much lesser degree, i.e., togreen in previously notch-bottom red areas 21, light blue in previouslygreen areas 22A and to no weakness in previously light blue areas 22B.In fact, a table of FIG. 6, which includes data from finite elementanalysis of prior-level frame 12 and the improved frame 120 of level 100of this invention, shows that the improved frame 120 is 180% strongerthen prior frame 12 without the internal horizontal and vertical walls30 and 35.

As seen in FIGS. 3 and 4, internal horizontal and vertical walls 30 and35 form a quad-box structure of a superior strength. It should be notedthat during manufacturing of the inventive level 100, the thickness ofthe frame-forming walls has been reduced. Surprisingly, despite suchthinning of the walls, the strength of the frame increased. This waspartially explained by decrease in the overall weight of the frame 120which resulted in static improvement and the frame impact performance.In addition to the improved level performance characteristics, suchthinning of the walls provides reduction in material used whichtranslates in lower product cost.

It is also important to note that specific positioning of the internalhorizontal wall 30 at bottom 21 of central-vial notch 20 is importantfor achieving such improved strength.

Another important aspect of the present invention is that suchpositioned internal horizontal wall 30 serves for accurate secureinstallation of the central vial 50. During manufacturing of the levelframe 120, top and bottom measuring walls 130 and 140 and an uppersurface 32 of internal horizontal wall 30 within central-vial notch 20all simultaneously undergo a milling by a computer-numerical controlmachine (CNC). The CNC milling during a single operation ensures thatall three surfaces are parallel to each other. Thus, upper surface 32 ofinternal horizontal wall 30 is parallel to top and bottom measuringwalls 130 and 140, as seen in FIG. 7.

Such accurately machined upper surface 32 of the internal horizontalwall 30 forms a reference shelf 33 for precise installation of centralvial 50 along vertical axis 53. As shown in FIGS. 8-11, vial 50 isplaced in a cradle 51 and mechanically mounted to upper surface 32 ofreference shelf 33 with mechanical fasteners such as screws 52.

Because of the accuracy in machining of reference shelf 33, there is noneed for manual calibration or adjustment in the positioning of centralvial 50 with respect to measuring surfaces 130 and 140. Such advance inthe central-vial installation provides great improvement inmanufacturing processes by substantially reducing manual labor. In priorlevels, each vial was secured to frame 12 by using an epoxy-basedlocking system. Each such vial was individually calibrated and only thenpermanently secured to frame 12. A number of problems is associated withsuch prior method of vial installation. One is that the need forcalibration of the vial prior to permanent securement involves manuallabor which increases costs for manufacturing and requires specialquality-control procedures. Another problem is that over time due tovariations in temperature or humidity adhesives tend to change itscharacteristics which may contribute to changes in positioning of thevial as well as in weakening of the vial attachment to the frame. Ininventive level 100, vial 50 is accurately secured to frame 120 withoutany glue, but only with mechanical fastening against precisely machinedreference surface 33 which does not change overtime.

Such mechanical securement of central vial 50 also involves an externalbrace 60 which is secured over central region 170 of level frame 120, asseen in FIGS. 9-15. External brace 60 includes two plates 61 each ofwhich spans the entire surface of the respective vertical side wall 180.External brace 60 is preferably made from cast aluminum and ismechanically secured to the frame with screws 62 which extend throughapertures 63 in sidewalls 180 and internal vertical wall 35.

Such external brace 60 completes mechanical fastening of the centralvial 50 to frame 120 by an additional fixing of vial 50 in a horizontalplane 54. As best seen in FIGS. 12-16, brace sandwiches a flange 55 of avial frame 56 such that vial 50 is securely held in front-to-back,up-and-down and left-to-right directions.

Furthermore, external brace 60 provides an additional reinforcement ofcentral region 170. In fact, the sandwiching of the central region byexternal brace 60 substantially eliminates the weakness in that area.Indeed, FIG. 17 illustrates that tests showed that previously weakest(red) areas in bottom 21 of notch 20, as seen in FIG. 2 showing priorlevel 10, are just slightly weakened (light blue) in improved level 100which includes external brace 60. The areas, which in prior level 10were substantially weak (green) or weakened (light blue), in improvedlevel 100 (seen in FIG. 17) exhibit similar strength as the strongestareas of frame 120 where no material removal occurred.

Moreover, the table of FIG. 18, which includes data from testing ofprior level 10 and improved level 100, shows that improved level 100 is300% stronger then prior level 10.

The manufacturing of the improved inventive level 100 also includes CNCmilling of openings 160 for plumb vials 40. While entirely removinginternal horizontal wall 30 in regions 160 of frame 120, such CNCmilling forms precise positioning references 36 in internal verticalwall 35 for installation of plumb vials 40, as seen in FIGS. 19 and 20A.This process allows for adhesive-free installation of plumb vials andensures precise positioning when the vials are secured within frame 120without any calibration or adjustment required. This is a greatimprovement over manufacturing of many prior box levels which requiredcalibration and adjustment of plumb vials. This process furthereliminates quality and longevity concerns associated with the use ofadhesive, as already discussed above. Vials installed within frame 120according to the inventive method will remain in their precise positionfor accurate reading over time.

FIGS. 20, 20A and 20B show that, in inventive box level 100, plumb vials40 are encased in a plumb-vial structure 41 made of a high-quality anddurability Xenoy* alloy which is a blend of semi-crystalline polyester(typically polybutylene terephthalate, PBT, or polyethyleneterephthalate, PET) and polycarbonate (PC). The Xenoy* alloy offersgreat impact resistance even at low temperatures, heat resistance, andoutstanding aesthetic characteristics. Xenoy alloys further offeroutstanding performance in applications that are exposed to harshconditions, or that require a high degree of toughness such asapplications for professional-construction levels. Furthermore, XenoyiQ* resins are created with polybutylene terephthalate (PBT)-basedpolymers derived from 85% post-consumer plastic waste, consuming lessenergy and yielding less carbon dioxide (CO2) in their manufacturingthan traditional resins. It is seen that the use of Xenoy* alloyspresent many advantages over standard acrylics often used in plumb-vialcasings.

In levels of substantial lengths such as forty-eight inches and greater,plumb vials are positioned at substantial distance from user's eyes.FIG. 21 shows how in some prior levels plumb-vial mounting structuresmay block the view for reading of the plumb vial.

FIGS. 19-23 illustrate another aspect of the present invention whichprovides improved visibility of plumb vial 40. Such improved visibilityis achieved by an inventive configuration of plumb-vial mountingstructure 41 includes an elongate inclined ramp 42 sloping from aboutthe side-wall surface at a reduced angle toward a plumb-vial window 43.Plumb-vial structure 41 has a viewing-end region 47A and an opposite-endregion 47B, the viewing-end region 47A including elongate ramp 42sloping along a level-longitudinal axis 101 toward plumb vial 40 with aninclination angle 400 permitting vial viewing from shallow angles 401.Such reduced angle 400 of inclination facilitates user's viewing ofplumb vial 40 from about central region 170 of level 100 or even fromfarther distance, as seen in FIG. 30. FIG. 20B best shows angle 400being 8.65° and as little as 5°. Vial opening 43 also has an elongateconfiguration of an inner portion 44 on the side of the level centralregion 170. Such elongation allows spacing of vial 40 away from ramp 42.As further seen in FIGS. 22 and 30, such spacing in cooperation withelongate inclined ramp 42 compensates for the extended viewing distanceand provides improved visibility of vial 40 for the necessarymeasurement readings.

The term “shallow,” as referred to the viewing angle 401, means thatsuch angle is closer to the 0° plane (of the major level sidewallsurface) than to the 90° plane (perpendicular to the level sidewalls).Angles 401 are preferably slightly above sidewall surfaces such that thevial becomes visible at a little over angle 400 of sloping ramp 42 shownin FIGS. 20B and 32.

Plumb-vial window 43 includes lenses 48 made of “bullet proof” Lexan*material. Such lenses provide further durability and impact resistanceof improved level 100.

FIGS. 20A and 20B show that plumb-vial structure 41 includes first andsecond side portions 411 and 412. Each side portion 411 and 412 ispositioned along one of level sidewalls 180. First side portion 411includes a high-friction region 46 extending from first side portion 411outwardly beyond an outmost sidewall portion 190, as best seen in FIG.24, for gripping a work surface. High-friction region 46 is preferablymade of rubber molded over the Xenoy* alloy. Rubber portions 46 extendbeyond the outmost vertical side surface 190 of that side of level 100to allow gripping of a work surface against which level 100 ispositioned for measurements.

FIG. 23 further shows an improved end cap 70 which is made with an ABSmaterial on the inside and an outside rubber coating over the ABSmaterial. The rubber coating provides an improved shock absorption evenif the level 100 is dropped from a substantial height. As seen in FIGS.23 and 25, outside rubber coating of end cap 70 includes a slightlyraised section 71. While raised section 71 does not extend beyond theoutmost vertical side surface 190 of that side of level 100, such raisedrubber section 71 facilitates gripping of a vertical surface againstwhich level 100 may be leaned against during a break between jobs, asseen in FIGS. 26 and 27.

As further seen in FIG. 25, end cap 70 is held to frame 120 with twocast aluminum mounting plates 72 which are mechanically secured to frame120 with screws 73. Such secure screw attachment also permits end caps70 to be removed by simple disengagement of screws 73. While the removalof end caps 70 requires use of additional tools such as screw driver,when necessary, this removable end-cap assembly accommodates precisemarking of the work surface even along corners. Each end cap 70 also hasan enlarged hang hole 74 which allows for quick hanging of level 100 onthe job site.

As with the plumb-vial casing, a hand grip 80 seen in FIG. 28 is alsomade from Xenoy iQ* alloy which is a material used in car bumpers and isvery strong in all temperatures, chemical resistant and UV stable. Asseen in FIG. 29, hand grips 80 are made with an enlarged hole 81 toaccommodate gloved hands and to reduce fatigue.

The invention claimed is:
 1. In a level including (a) an elongateone-piece frame with a hollow interior defined by two sidewallsextending between top and bottom horizontal walls, each horizontal walldefining corresponding top and bottom parallel measuring surfaces andtop and bottom interior surfaces, (b) a topnotch formed by removal of atopwall section and adjacent sections of sidewalls, and (c) a centralvial within the topnotch, the improvement comprising the one-piece frameincluding an integral inner vertical wall extending between thesidewalls within the frame hollow interior and having inner top andbottom ends each of which extends from the corresponding one of thehorizontal top and bottom interior surfaces thereby reinforcing thehollow frame weakened by the removal of the topwall section to form thetopnotch.
 2. The level of claim 1 wherein: the frame defines an end-vialopening formed through the sidewalls and the inner vertical wall; thevertical wall forms calibration-free end-vial-positioning references;and an end vial is supported within the end-vial opening in accurateorientation without calibration.
 3. The level of claim 2 wherein: thesingle-piece frame further includes an inner horizontal wall extendingbetween edges of the topnotch; the inner horizontal wall provides acentral-vial reference surface defining a notch-bottom formed in theinner horizontal wall parallel to the top and bottom measuring surfaces;and the central vial is supported against the cental-vial referencesurface in accurate orientation without calibration.
 4. The level ofclaim 3 wherein the central vial is secured with respect to the innerhorizontal wall by mechanical fasteners.
 5. The level of claim 3 whereinthe hollow frame is an extrusion with the top and bottom walls and theinner horizontal wall being integral with the sidewalls thereby furtherreinforcing the frame weakened by the topnotch removal of the topwallsection.
 6. The level of claim 5 further including an external bracehaving: a pair of plate members each against one of the sidewalls andeach substantially spanning a respective one of the sidewalls; and afastening member extending through the sidewalls and pulling the platemembers toward each other to sandwich the sidewalls therebetween,thereby further reinforcing the frame weakened by the topnotch.
 7. Alevel including an elongate one-piece extruded frame supporting at leastone vial, the one-piece extruded frame comprising: a surroundingexterior wall defining a hollow frame interior and including top andbottom measuring surfaces defined by topwall and bottomwall portionseach extending between two sidewall portions; and an inner wall spanningthe frame hollow interior from the topwall portion to the bottomwallportion thereby reinforcing the hollow frame.
 8. The level of claim 7wherein the one-piece frame further includes an inner horizontal wallspanning the frame interior between the sidewalls thereby furtherreinforcing the frame.
 9. The level of claim 8 further including: the atleast one vial includes a central vial within a topnotch formed byremoval of a topwall section and adjacent sections of sidewallsincluding notch-defining bottom and side edges.
 10. A method forcalibration-free manufacturing of a level including an elongateone-piece frame with a hollow interior defined by (a) top and bottomhorizontal walls each defining corresponding top and bottom parallelmeasuring surfaces and top and bottom interior surfaces and (b) twosidewalls extending between the top and bottom walls, the improvementcomprising: forming the one-piece frame including an integral innervertical wall extending between the sidewalls within the frame hollowinterior and having top and bottom ends each of which extends from thecorresponding one of the horizontal top and bottom interior surfaces;forming a vial opening through the sidewalls and the inner verticalwall; forming vial-positioning references in the inner vertical wall;placing a vial structure within the vial opening with a vial orientedaccording to the vial-positioning references in the inner vertical wallwhich assure vial accurate orientation without calibration; and securingthe vial structure with respect to the sidewalls of the frame.
 11. Themethod of claim 10 wherein the steps of forming the vial opening andforming vial-positioning references are performed simultaneously by asingle step of CNC machining through the sidewalls and the innervertical wall to assure calibration-free accuracy of the vialorientation.
 12. The method of claim 10 wherein the vial is secured withrespect to the frame with mechanical fasteners and free of adhesive. 13.The method of claim 10 wherein the single-piece frame includes anintegral inner horizontal wall extending between the sidewalls atnotch-defining bottom edges, the method further includes the steps of:forming a central-vial receiving topnotch by removal of a topwallsection and adjacent sections of sidewalls; simultaneously forming threeprecisely parallel to each other surfaces including top and bottommeasuring surfaces and a notch-bottom surface respectively formed in thetop and bottom walls and the inner horizontal wall; placing acentral-vial structure on the notch-bottom surface which assurescentral-vial accurate orientation without calibration; and securing thecentral-vial structure with respect to the frame.
 14. The method ofclaim 13 wherein the step of simultaneously forming parallel surfaces isby a single step of CNC machining of the top and bottom horizontal wallsand the inner horizontal wall.
 15. The method of claim 13 wherein thecentral-vial structure is secured to the inner horizontal wall withmechanical fasteners and free of adhesive.
 16. The method of claim 13including the further steps of: providing an external brace including apair of plate members each configured to substantially span one of thesidewalls; positioning each plate member against a respective one of thesidewalls; and securing the external brace to the frame with a fasteningmember extending through the sidewalls and pulling the plate memberstoward each other to sandwich the sidewalls therebetween, therebyreinforcing a central frame portion weakened by the topnotch.
 17. Themethod of claim 13 wherein the hollow frame is an extrusion.